1. Field of the Invention
The present invention relates to a concentration method of a fine particle dispersion using a micro-flow channel and a concentration apparatus of a fine particle dispersion comprising a micro-flow channel.
2. Description of the Related Art
In business fields handling fine particles, specially, food product production, production of fine particle products such as pigments and polymers, sludge treatment as environmental protection technology, fine particle dispersions are delivered and fine particles are collected in the form of slurries or solid state. Particularly, if a fine particle dispersion has a low concentration, the transportation efficiency is low and therefore, it is required to concentrate such a dispersion. As concentration methods commonly used, methods of centrifugal separation utilizing sedimentation, filtration, drying and evaporation, and classification are used, however, basically these methods are carried out in a batch manner and accordingly, the methods require not only many steps, but also the recovery efficiency is low. Further, normally, the methods require a high energy and a long processing time. As a method of transporting, adhering and recovering fine particles in a fine particle dispersion, there is a method of utilizing electrophoresis. For example, a method in which silica fine particles are dispersed in an aqueous alkaline solution, are negatively charged by applying an electric field between the polishing tool and a counter electrode, is used, so that the particles are adhered to a polishing tool to improve specular polishing. However, this method has an extremely poor efficiency and requires a long time and a high energy.
On the other hand, methods of carrying out chemical reactions and unit operation in micro regions have been investigated in recent years. In relation to this, methods and apparatuses of extraction, separation, mixing and particle formation focusing on a short diffusion time have been proposed. Among these methods, as a method in which electrophoresis is applied to a micro device, a method of transporting an extremely small amount of a sample by applying an electric field in a similar manner to a capillary electrophoresis chip by which an electric field is applied to a sample in a micro flow channel and the sample is electrophoretically migrated by the electric field for detection by a photo-detector is proposed (e.g. Japanese Patent Application Laid-Open (JP-A) No. 9-304338). However, the method is used for transporting an extremely small biochemical substance such as a protein or DNA and is not used for transporting fine particles, and cannot be applied to concentration of a fine particle dispersion.
As described, there is no method or apparatus made available for concentrating a fine particle dispersion continuously in a low number of steps, at a high recovery efficiency, and low energy without any problems.